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THE UNITY OF THE PHYSICAL WOELB. 



I. FACTS OF CO-EXISTENCE. 



By ALEXANDER WINCHELL. 



[Extracted from the Methodist Quarterly Review for April, 1873.] 



CJHU 1 



u^ 6 






JA 



ETHODIST 

Quarterly Eeview. 

APEIL, 1873. 



Art. I.— THE UNITY OF THE PHYSICAL WORLD 

Le del Geologique. Prodrome de geologie comparee. Par Stanislas Meunier. 

Paris. 1871. 
Die Spectralanalyse in Hirer Anwendung auf die Stoffe der Erde und die Natur der 

Himmelskorper, Gemewfdsslich dargestellt. von Dr. H. Schellen. Zweite Auf- 

lage. Braunschweig. 1871. 
The Heavens. An Illustrated Hand-book of Popular Astronomy. By Amedee 

G-uillemin. Edited by J. Norman Lockyer, F.R.A.S., F.R.S. Fourth edition. 

Revised by Richard A. Proctor, B.A., F.R.AS. New York. 1871. 
Cows elementaire d' ' Astronomie. Par M. Ch. Delatjnay. Paris. 1870. 
Le Soleil. Expose de principales decouvertes modernes sur la structure de cet astre. son 

influence dans Vunivers et ses relations avec les auires corps celestes. Par le P. Sec- 

CHi, S. J. Paris. 1870. 
The Sun : Ruler, Fire, Light, and Life of the Planetary System. By Richard A. 

Proctor, B.A., F.R.AS. London. 1871. 

The six works whose titles are above cited may serve to index 
a recent progress in cosmical physics which constitutes one of 
the most noteworthy features of the science of the nineteenth 
century. They report additions made to our knowledge of 
the constitution and history of the heavenly bodies during the 
last ten or fifteen years scarcely equaled by the acquisitions 
of any previous decade and a half. This recent progress, vast 
as it is, yields in interest to the promises of the new status 
which has been conferred upon scientific investigation. The 
sciences are out of their ruts. The time is past when each 
specialist can spend a life-time over his chosen problems with- 
out arousing the interest of laborers in other fields, or hope to 
Fourth Series, Vol. XXV.— 12 



182 Unity of the Physical World. [April, 

attain to prompt and valid solutions without calling them to 
his aid — each with such knowledge and appliances as his own 
labors have placed at his command. A new sympathy among 
the sciences is awakened. They are beginning to reach a com- 
mon ground, and to reflect the unity which belongs to the uni- 
versal system of truth. The sciences are becoming broadened 
and liberalized; their metes and bounds are less distinctly 
marked ; like the colors of the rainbow, they mutually overlap 
and blend, and lose all separate identity, save in their dominant 
features, because, like the colors of the rainbow, they are only 
the outcome of a varied unity. 

The astronomer, seeking for a knowledge of the heavenly 
bodies, first lays the theory of optics under contribution to 
improve his power of seeing. Then he finds himself in the 
midst of a universe animated by mechanical foffces, and execut- 
ing its activities through geometrical forms and along mathe- 
matical lines. The astronomer must needs be an optician and 
a geometer. Next, optics places at his service a peculiar 
instrument, which, by a marvelous resolution of light from the 
sun and stars, presents a body of phenomena utterly unintelli- 
gible till chemistry steps in and introduces to his acquaintance 
the guests of the laboratory. Now he calls over the names of 
sodium, hydrogen, and barium, and they respond to him from 
star and nebula. 

The geologist, beginning with the attempt to unravel the 
structural arrangement of the materials of the earth, soon dis- 
covers that it has had a history — that he must endeavor to 
trace the successive monuments of this history back to its com- 
mencement. He calls upon the mineralogist to expound the 
constitution of the rocks — the solid records of the history whose 
reality is disclosed ; and the chemist appears, to reduce all 
things to five or six dozen simples. Soon he discovers evi- 
dences of ancient heat, and finds himself involved in experi- 
ments upon the actual escape of heat from the earth, and 
abstruse mathematical calculations in reference to the neces- 
sary or possible rate of cooling from any assignable condition.* 
He penetrates back to a molten state, and here he catches the 
utterances of the astronomer, gazing through his tube at the 

• * See especially the researches of Poisson, Fourier, Hopkins, and Thomson, (Sir 
William.) 



1873.1 Unity of the Physical World. 183 

sun and the stars. u Igneous vapors," "molten worlds," are 
reported from the depths of space. " And here," responds the 
geologist, " in the very world which is our observatory, behold 
a planetary slag which, some time back, was a ' molten world,' 
and why not an ' igneous vapor ? ' " Geology and astronomy 
join hands and set out in the search for formative worlds 
which may serve as types of ancient stages of terrestrial history. 
Later in that history are found the relics of organized creatures, 
upon which existence has been conferred as the world was fitted 
for them. The rocky beds of the earth's crust are their tombs, 
which no sacred scruples restrain the geologist from exploring. 
With the zoologist upon his right, and the botanist upon his 
left, he walks among these tombs, and as his companions pro- 
nounce the names and alliances of these relics of the organic 
world he assigns them their respective places in the system of 
terrestrial preparations, and writes down their respective epochs 
in the unfolding of the pre-Adamic ages. Thus geology is the 
resultant of mechanics, thermotics, mathematics, mineralogy, 
chemistry, astronomy, zoology, and botany, and of all the 
aids which these sciences summon to their completion and 
efficiency. 

It is this conception of the sources of geological information 
which M. Meunier has brought into requisition in seeking to 
retrace the evolution of our world to its beginning. He sees 
in the present condition of the masses of cosmical matter pict- 
ures of a former condition of the earth. Drawing upon the 
body of astronomical facts, which nowhere find a completer pop- 
ular statement than in the works of Guillemin, Delaunay, or 
Chambers,* he presents us an array of evidences demonstrat- 
ing a unity, not only of the physical sciences, but of the domin- 
ion of the forces of matter, and the intelligence which their 
activities reveal throughout the utmost breadth of the visible 
universe. The work of Father Secchi, of the " Eoman Col- 
lege," is a charming volume, setting forth in fuller detail 
every thing which is known respecting the sun as a cosmical 
body. It embraces the results of the Jesuit father's original 
observations and speculations upon the sun and its relations to 
the other heavenly bodies, the earliest records of which may 
be found scattered through the volumes of the Comtes rendus 

♦Chambers' (Geo.F.) "Descriptive Astronomy." 8vo M pp. 816. Oxford, 1867. 



184 Unity of the Physical World. [April, 

of the Academie des Sciences at Paris from 1863 to 1870. 
Proctor's work, which appeared almost simultaneously, is writ- 
ten with the same object in view, and, like the other, contains 
a large infusion of originality. The most marvelous recent 
advances in cosmical physics have been attained through the 
use of the spectroscope, which has, brought us to a knowledge 
of the chemical constitution of the stars — a mysterious analysis 
of matter from which we are separated by millions and billions 
of miles. The philosophy and forms of the spectroscope, and 
its applications in spectral analysis, are completely set forth and 
magnificently illustrated in the work of Schellen, which has the 
further merit of being the most recent work of its class — a 
prime quality in reports of scientific progress, characterized by 
such strides as have been taken by spectroscopic research.* 

A survey of the field of scientific truth, as set forth in these 
works, is well adapted to impress the reader with a conviction 
that all parts of the visible universe appertain to one system 
of things ; that all have proceeded from one commencement, 
have been actuated by one impulse, have experienced one his- 
tory, are bound to a common destination ; and that each ex- 
emplifies, at every moment of its existence, a stage of evolution 
which is embraced in the life of every other. These facts, so 
largely reinforced by recent discoveries, reflect important light 
upon the question of evolution in the material world ; but we 
propose to confine our attention to the scientific proofs of the 
co-existent unity of the system of matter. 

I. The order and uniformities of the solar system. 

(1.) Orbital motions. When we lift our thoughts to the con- 
templation of the planetary system, of which our earth is a 
member, we are profoundly impressed by the harmony of those 
silent but majestic movements executed in the depths of space. 
The noiseless flight of over a hundred worlds about a common 
center, passing and repassing without collision or mistake, like 
partners moving through the orderly mazes of a dance, is a 

* This work has been translated into English by the daughters of the astrono- 
mer Lassell, and edited, with notes, by William Huggins. An edition of the trans- 
lation is published by Van Nostrand, New York. The subject is also explained in 
the works of Proctor and Secchi, cited above. Roscoe's "Spectrum .Analysis " is 
also republished in New York; and information conveniently accessible maybe 
found in Chatfield's '• University Series," No. VII, and Lee & SheparcVs "Half- 
Hour Eecreations in Popular Science," Nos. Ill, TV aud Y. 



1873.] Unity of the Physical World. 185 

spectacle well calculated to awaken the emotions of every soul 
not dead to the sentiment of the sublime. 

Eight major planets are known to belong to this system, be- 
sides one hundred and twenty-one * minor planets, or asteroids, 
already discovered. These one hundred and twenty-nine bod- 
ies all possess a common orbital motion, from west to east, 
around the same center, indicating at once that they all belong 
to one system, regulated by a common law. This conviction is 
strengthened when we observe that the several orbits possess 
the same mathematical properties, and that the planets move 
with corresponding velocities in corresponding parts of their 
orbits. The orbits, for instance, as expressed by the first law 
of Kepler, are all ellipses, with the sun situated in one of their 
foci ; while the motions of all the planets are most rapid when 
in their lower apsides — or those parts of their orbits nearest the 
sun — and slowest at the opposite extremities of their orbits. 
Moreover, it appears from mathematical demonstration that 
the orbital motion of every planet is capable of being caused 
by the action of two forces — the one a tangential impulse, giv- 
ing the planet a motion through space, which, from the inertia 
of matter, would be continuous, the other a constant force, act- 
ing in the direction of the center of gravity of the sun, with an 
intensity varying directly as the masses and inversely as the 
square of the planet's distance from the sun. 

In the next place it will be observed that these orbits all lie 
in nearly the same absolute plane, suggesting that the planet- 
ary movements have all been generated under uniform circum- 
stances. They do not present the spectacle of a swarm of bees, 
darting in every conceivable direction through space, each actu- 
ated by an independent impulse, but rather the consonant and 
rhythmical. movements of a fleet of ships wafted onward by a 
common breeze. 

The orderly arrangements of the planets in respect to dis- 
tances from the sun must also be noted. They revolve at reg- 
ularly graduated distances. ~Ro clashing can ever occur. 
Moreover, there arg mathematical relations existing between 

* The one hundred and eighteenth was discovered, March 15, 1872, by Dr. 
Luther, of Bilk; the one hundred and nineteenth', April 3, by Prof. Watson, of Ann 
Arbor; the one hundred and twentieth, April 10, by Borelli, of Naples; and the 
one hundred and twenty -first, May 12, by Watson. 



186 Unity of the Physical World. [April, 

their velocities, periodic revolutions, and distances from the sun, 
which are the same for all the planets, and show that the same 
physical laws extend throughout the solar system. These rela- 
tions are known as the second and third laws of Kepler, and 
are thus enunciated : 

2. The radius vector of any planet (that is, the line from the 
planet to the center of its motion) sweeps over equal areas in 
equal times. 

3. The squares of the periodic times of the planets are to 
each other as the cubes of their mean distances from the sun. 

These relations are absolutely fixed, and they demonstrate 
that one dominion extends to the utmost limits of the solar 
system. 

(2.) Satellites. A further correspondence among the several 
members of this system is the presence of secondary planets re- 
volving about iive of them. The earth is accompanied by one 
satellite, Jupiter by four, Saturn by eight, Uranus by six or 
eight, and Neptune by one or more. Each satellite revolves 
about its primary in an elliptic orbit, having the primary planet 
in one of the foci. The direction of the orbital motion of the 
satellites, like that of the primaries, is from west to east — ex- 
cept that the satellites of Uranus, and probably of Neptune, 
exhibit a retrograde motion, from east to west. Could we sup- 
pose that the direction of the original motion, in the systems 
of Uranus and Neptune, was from west to east, and that, by 
some convulsion, those systems had been bodily overturned, it 
is apparent that the same actual motion of the satellites, in ref- 
erence to their primaries, would become a reversed motion in 
reference to the earth, or any other fixed point in space. This 
may be illustrated to the eye by the use of a watch. "When 
the watch lies upon its back, the extremities of the pointers 
represent satellites having a direct motion. In that part of 
their circuit nearest the observer that motion is from right to 
left ; or, if the person be facing southward toward the belt, 
where the planetary bodies appear, the motion is from west to 
east. If now the watch be inverted, so as to lie on its face, the 
extrem ties of the pointers move from left to right, a motion 
which, transferred to the- southern heavens, as before, becomes 
retrograde — that is, a motion from east to west.* If it were 

* The orbital motions here referred to must not be confounded with the appar- 



1873.] Unity of the Physical World. 187 

admissible, therefore, to suppose that, since the birth of the 
systems of Uranus and Neptune, they have undergone an inver- 
sion in space, it appears that, notwithstanding the anomaly 
which they present, their rotations in respect to themselves are 
in the same direction as the motions of the other systems ;* 
and they are thus original parts of what appears to be a com- 
mon effect traceable to a general cause responsible for the uni- 
form movements executed throughout the solar system. 

(3.) Axial motions. In the next place, all the planetary bod- 
ies revolve upon their own axes. It is further remarkable that 
the axial motions are all in the same direction, and that this 
direction is the same as that in which the planets revolve in 
their orbits. It is probable, however, that Uranus and Nep- 
tune have a retrograde motion, like their satellites ; but this, 
as before, may be explained on the hypothesis of an inversion 
of those planets. The sun, also, and moon, have axial rotations 
in the same direction. We witness, then, the spectacle of prob- 
ably more than a hundred cosmical bodies, all spinning about 
their axes with silent and ceaseless velocity, as if some com- 
mon cause had affected all alike. It is as if the Almighty 
Hand had taken each in succession and set it whirling, as the 
boy spins his top upon the floor — each dancing off in due order, 
but with uniform motion, until the last two are reached, when 
the planetary tops were inverted, and set to spinning upon their 
handles. There could scarcely be a spectacle accessible to 
human intelligence more convincing than the planetary mo- 
tions, that one plan and one purpose reign throughout the realm 
of the solar system. Such Kepler confessed to be the impres- 
sion made upon his mind by the contemplation of the harmo- 
nious movements of the heavenly bodies ; and such was the 
confession of Newton. " The wisdom of the Lord is infinite," 
says Kepler, " as are also his glory and his power. Ye heav- 

ent daily movem ent of the heavenly bodies from east to west, caused by the rota- 
tion of the earth upon its axis. These orbital motions, as in the case of our own 
moon, are revealed by the appearance of the same planet, on each successive even- 
ing, a little further eastward among the constellations. 

* This hypothesis is favored by the circumstance that the inversion of the sys- 
tem of Uranus is not complete — having been carried but little beyond a quarter of 
a circumference. We might homologize the attitude of these satellites by saying 
that they have an inclination of about one hundred and one degrees to the plane 
of their ecliptic, while our moon has an inclination of only five degrees. 



Unity of the Physical World. [A pi 



ens, sing his praises ! Sun, moon, and planets, glorify him in 
your ineffable language ; praise him, celestial harmonies, and 
all ye who can comprehend them!"* Such language sounds 
more like a psalm of David than the conclusion of a learned 
scientific treatise. " The Master of the heavens," says New- 
ton, " governs all things. ... He is the one God and the 
same God every-where and always." . . . f 

(4.) Planetary Forms. The rain-drop takes the form of a 
sphere, and so does the molten lead falling from the summit 
of the shot-tower. The physicist informs us that this is the 
natural form of every detached body of matter whose particles 
are free to adjust themselves according to an inherent law of 
the mass. A moment's reflection on the nature of a central 
force will convince any one that no other form is possible 
among a body of particles each equally drawn toward a com- 
mon center of gravity. But what interests us most is the fact 
that the planetary bodies, hundreds and thousands of millions 
of miles distant from our earth, have felt and manifested the 
urgency of the same law. The planets, primary and second- 
ary, have all shaped themselves after the model of the rain- 
drop. We have so long heard that the planetary bodies are 
spherical that we cease to reflect on the meaning of the fact ; 
but this common form implies that the totality of matter with- 
in the orbit of Neptune subsists under the government of one 
empire whose laws are enforced equally in the midst of a New- 
foundland fog, in the immense globe of the solar flame, and in 
the solid body of Neptune shivering on the frozen verge of the 
realm of planetary existence. 

(5.) Physiographic Features of the Planets. The super- 
ficial characters of the planetary bodies, so far as we have been 
able to learn them, present marked analogies with those of our 
own planet. The surface of the moon, as is well known, is 
distinctly diversified by mountain, valley, and plain. A large 
number of the summits present crater-like forms with enormous 
gorges variously grouped about, and have generally been re- 
garded as monuments of extinct volcanic action. In respect 
to climate the planet Mars furnishes distinct evidences of a 
close analogy with the earth. His succession of seasons must 

* Kepler : Harmonices Mundi, libri quinque. 

f Newton: Philosophies, naturalis principia mathematica. 



1873.] Unity of the Physical World. 189 

be similar to our own. It is alternately winter and summer in 
each hemisphere. Accordingly, the shining mantle of snow is 
seen to gradually extend itself toward the equator in the hem- 
isphere turned away from the sun, and to gradually retreat 
during the other half of the Martial year. The snow mantle 
which covers the polar regions of the earth must exhibit a sim- 
ilar annual advance and retreat to observers upon the planet 
Mars. Finally, the last-named planet, which seems, indeed, in 
many respects, to be the nearest analogue of the earth, offers a 
distribution of land and water which strongly suggests the 
hydro-graphic arrangements of our own planet. The equatorial 
regions are mainly occupied by four large continents, which 
are separated by vast oceans diversified by islands and con- 
nected by straits, protruding, in some places, broad gulfs into 
the borders of the land, and in others sending out long tortu- 
ous inlets, one of which attains the length of -3,000 miles, and 
must be essentially similar to the mediterranean channel 
which connected the Gulf of Mexico with the Arctic Ocean in 
the Mesozoic age of terrestrial history. 

The atmosphere of this planet possesses physical properties 
similar to our own. It is charged with vapors and gases, and 
floating clouds make beautiful its evening sunsets and its 
morning sunrises, and not unfrequently fierce storms sweep 
over the surface of the planet, obscuring it to telescopic 
vision.* 

The surface of Mercury is known to be diversified by valleys 
and mountains, and one of the latter is thought to be no less 
than eleven miles in height. Schroter believed that he de- 
tected the existence of an active volcano. Venus is believed 
to be enveloped in an atmosphere, and to present great ine- 
qualities of surface, exceeding even those upon the surface of 
Mercury. During the transits of these planets across the sun's 
disc several observers have reported seeing grayish light spots, 
which rotate with the planets. Schroter, Harding, Fritsch, 
and Moll have seen them in transits of Mercury, and at least 
one observer detected such a spot during a transit of Yen us. f 

*Lockyer: "Mem. Royal Astronom. Soc," vol. xxxii, p. 183. On the analogies 
of Mars ancLthe Earth see, besides the works cited, Proctor: "Other Worlds than 
Ours," chap. iv. 

\ Chambers : " Descriptive Astronomy," book ii, chap, iv 



190 Unity of the Physical World. [April, 

Such spots possibly mark the sites of active volcanoes. Jupi- 
ter is believed to be furnished with an atmosphere in which 
float vast changing belts of watery vapor, and similar opinions 
are entertained in reference to the body of the planet Saturn. 

Such are the most striking phenomena which evince the 
existence of a bond of relationship binding the members of 
the solar system in a unity. It seems impossible to contem- 
plate the variety and complexity of the movements of these 
planetary bodies, and the incessant responses which they yield 
to each other's perturbating influences, without being struck 
with admiration of the harmony, security, and stability with 
which they move in their appointed courses, and the simplicity 
of the primal forces to which all these phenomena may be 
traced. Given the force of gravity and a single impulse, and 
the life-time of a planet can be charted. Supposing the earth 
created and placed at the distance of 91,500,000 miles from 
the sun, gravity alone would produce a fall upon the sun. 
But if at the same instant, or at any time during its fall, an- 
other force, however slight, should give the earth a push in a 
direction across its line of descent, the earth would pass by the 
sun, and fly onward to the distance of 91,500,000 miles beyond, 
when it would return and pass the sun on the opposite side, 
and thus an orbital motion would be established. If the tan- 
gential impulse were nearly equal to the centripetal attraction, 
and directed at right angles to the line of descent, the elliptic 
path described would approximate nearly to the actual form of 
the earth's orbit. If the line of the tangential force should not 
pass through the earth's center of gravity, a rotation would be 
generated as well as an orbital motion. 

Further, since the several planets revolve about the sun in 
the same direction, and in nearly the same plane, it is apparent 
that the tangential impulse which may have imparted to each 
its orbital and axial motions must have acted in one plane 
and in the same direction ; and though it seems to have acted 
along lines at different distances from the sun, it is conceiv- 
able that it may have been a single cause which, at the peri- 
ods of birth of the several planets, may have assumed these 
different positions in accordance with some intelligible law 
of change. 

Now science has long reflected upon these circumstances, 



1873.] Unity of the Physical World. 191 

and has framed a hypothesis in accordance with which these 
varied movements of the. planetary bodies may be traced back 
to a common condition, molded and actuated by a common 
impulse, and launched in accordance with a uniform plan into 
that state of delicate equipoise between centripetal and cen- 
trifugal forces which so excites our admiration and amazement. 
We say it was originally a " hypothesis," as the doctrine of 
gravitation was originally a hypothesis; but like that hypothe- 
sis, this has gradually developed into a settled doctrine of 
science, which is gaining the general acceptance of the best 
physicists and astronomers throughout the world. It is not 
our purpose at present to furnish an exposition or systematic 
proof of the hypothesis, but simply to suggest the culmination 
of a series of phenomena and relations which bind our whole 
assemblage of planetary bodies in the intimate and inseparable 
unity of a single family. 

II. Extension of the laws of the solar system to the fixed stars. 

(1.) Distances of the stars. Vast as the interval from the sun 
to the remotest planet, it is insignificant compared with the 
gulf of space which intervenes between Neptune and the fixed 
stars. Neptune is about 2,745,000,000 miles distant from the 
sun ; but Alpha Centauri, the nearest star, is removed 7.466 
times that distance, or 20,496,000,000,000 miles. It will con- 
vey some idea of the relative values of these numbers to state 
that if we represent the distance of Neptune from the sun by 
a line eight (7.8) inches in length, the distance of the earth 
from the sun will correspond to a line one quarter (0.26) of an 
inch in length, and the distance of Alpha Centauri will corre- 
spond to a line one mile in length. If we reduce the distance 
of Alpha Centauri to one hundred feet, the distance of Neptune 
would be eighteen ten thousandths (0.0018) of an inch, which is 
about one sixth the diameter of a human hair. 

On the same scale of representation as before, the star 61 
Cygni will be removed to the distance of 2.4 miles ; Vega, 5.9 
miles ; Sirius, the brightest of the stars, 6.1 miles ; Iota Ursse 
Majoris, 6.9 miles ; Arcturus, 7.2 miles ; Polaris, 13.7 miles ; 
Capella, 20.0 miles. These are the distances of stars scattered 
about the nearest outskirts of the firmament. The great mass 
of the fixed stars lies hundreds of times as remote as these. 
Sir William ITerschel believed that he reached with his great 



192 



Unity of the Physical World. 



[April, 



telescope, stars which lie 2,300 times the average distance of 
stars of the first magnitude, and jet we possess abundant 
evidence that throughout this vast realm stretches but one 
physical empire. 

TABLE OF DISTANCES FROM THE SUN.* 



Objects. 



Radii 

of Earth's 

Orbit. 



Millions of 
Miles. 



Propor- 
tional. 



Time for 

Passage of 

Light. 



Earth 

Neptune 

Aphelion, Donati's Comet. 

" Comet of 1861 C) 

Comet of 184400 

Alpha Centauri 

61 C} T gui 

Vega 

Sirius 

Iota Ursse Majoris 

Arcturus 

Polaris ... 

Capella 



1 
30 

238 

440 

4,000 

224,000 

550,920 

1,330,700 

1,375,000 

1,550,800 

1,622.800 

3,078,600 

4,484,000T 



91J 

2,745' 

22,000 

40,121 

368.000 

20,496,000 

50,409.000 

121.759^000 

125,812,000 

142,356,000 

148,486.000 

281,692.000 

410.286,000 



0.26 in. 

8.8 in. 

5 ft. 2 in. 
9 ft. 6 in. 
86 ft. 8 in. 
1 mile. 
2.4 mile. 

5.9 " 

6.1 " 
6.9 " 

7.2 " 
13.7 " 
20.0 " 



8 m. 18 sec. 

4 h. 9 m. 

33 h. 

61 h. 

20 d. 18 h. 

3.537 yrs. 

8.49 " 
20.87 " 
21.58 " 
24.41 " 
25.47 " 
48.46 " 
70.74 " 



(2.) Comets. Besides the planets belonging to our system, 
there are already known thirty-six mysterious bodies, called 
comets, which also revolve with regularity about the sun. 
Though the amount of matter which they possess is astonish- 
ingly insignificant, and their substance is of such tenuity that 
the light of the stars has been seen to shine through it, they 
move in their appointed orbits with nearly the same regularity 
as the ponderous planets, and all the phenomena of their mo- 
tions have been explained on the same physical theory. Some 
of these comets, in receding from the neighborhood of the 
sun, retire no further than the orbit of Jupiter ; others fly on- 
ward to the distance of Uranus; while Hal ley's comet travels 
338,000,000 miles beyond the orbit of Neptune, and occupies 
seventy- seven years in its revolution. Still others penetrate 
the starless void to greater depths, and yet signify their alle- 
giance to the laws of the solar system. Donati's comet has a 

* The quantities in this table have been calculated from Stone's corrected paral. 
lax of the sun, (8."91.) Should the earth's distance from the sun be taken at 
ninety-two millions of miles, the quantities in the last three columns, beginning 
with Neptune, will have to be increased yp- part of their value. The time re- 
quired for the passage of light from the sun to the earth is taken from Delaunay 
(Op. Cit, p. 331.) Sir John Hersehel puts it at 8 m. 13. "5. ("Familiar Lectures 
on Scientific Subjects," p. 227.) 



1873.] Unity of the Physical World. 193 

period of 2,100 years, and travels 229,000,000,000 of miles from 
the sun. The comet of 1811 has gone on a journey of 3,000 years ; 
the comet of 1680 is expected to be absent 8,814 years ; while 
the comet of July, 1844, is under pledge to report at the head- 
quarters of our system after an absence of 100,000 years ; 
During this journey it travels to the distance of 368,000,000,000 
of miles from the sun, and yet throughout the utmost limits of 
their flight these mysterious wisps of luminous vapor acknowl- 
edge every hour their allegiance to the central authority of our 
system. There is not a moment when the gentle influence of 
our sun ceases to be felt. Across the silent and measureless 
void the subtle power of gravitation manifests its presence as 
distinctly as in the falling acorn in the forest. 

These comets all move, of course, in elliptic orbits. A large 
majority of them possess a direct motion, and conform approxi- 
mately to the plane of the ecliptic. These are circumstances 
which intimate an alliance with our system, as well as a sub- 
jection to the general laws of matter.* 

But there are other comets which venture beyond the bound- 
ary line which separates the empire of our sun from some 
contiguous dominion. From time to time these unrecognized 
strangers plunge, unannounced, into the midst of our planetary 
system, hurry with excited haste to the neighborhood of our 
solar center, whirl round their perihelion, and dart forth again 
into the abyss of space, never to return. There can be little 
doubt that the non-periodic comets pass within the. influence 
of other solar centers, around which they swing with similar 
haste, to dart off again to the neighborhood of other suns. 
These strange comets move, while within the limits of our sys- 
tem, in accordance with the same laws as the periodic comets, 
and their places can be similarly calculated from day to day, 
and from week to week ; but as their paths are parabolic and 
hyperbolic curves, their very flight from the local government 
of our system is as much the subject of mathematical demon- 
stration as is the return of comets moving in elliptic orbits. It 
cannot be doubted that if they visit other suns it is to acknowl- 

* All comets moving in hyperbolic orbits also have a direct motion, and thus 
furnish other intimations of some connection between their history and that of the 
planetary bodies. Delaunay, however, (Op. Cit., p. 644,) is of the opinion that all 
comets are either strangers, or only naturalized denizens in the solar system. 



194 Unity of the Physical World. [April, 

edge still their allegiance to the supreme force of gravitation, 
and to travel in paths which might become as strictly the sub- 
jects of computation as the paths described by them outside 
the limits of our system.* 

Thus these wanderers range from sun to sun, from system to 
system, impelled ever by one force, regulated every-where by 
one government, weaving the visible universe into a compact 
w T eb of indissoluble relationships, f 

(3.) Stellar Phenomena. Still other intimations reach us. 
Viewed with the telescope, many of the fixed stars appear 
double. We know at least 6,000 of them. Not less than 650 
of the double stars are demonstrated to be real systems, phys- 
ically connected, revolving about a common center of gravity 
between them. The periods of their revolutions range from 
14 to 1,200 years. The following are examples: A pair in 
Coma Berenices is thought to have a period as short as 14 
years ; Zeta Herculis revolves m 36 years ; Sirius, in 49?- ; 
Zeta Cancri, in 59 ; Xi Ursse Majoris, in 61 ; Mu Coronse Bo- 
realis, in QQ ; Alpha Centauri, in 81 ; Pi Ophiuchi, in 92 ; 
Gamma Yirginis, in 150; 61 Cygni, in 520; and Gamma 
Leonis is thought to have a period of 1,200 years. 

These, also, are real orbital motions, manifested at such dis- 
tances that even light, traveling 186,000 miles a second, would 
require years to reach us. Not only that ; these orbits are also 
ellipses. Now there can be no orbital motion except under 
the action of centripetal and centrifugal forces: gravity and 
inertia are there. And since the velocity of rotation — to give 
a centrifugal force equal to the centripetal — must increase with 
the intensity of the centripetal, that is, the gravitating force, 
physicists have been enabled to calculate even the weight of 
distant suns revolving about their centers. Thus, we know 
that the mass of 61 Cygni is one third the mass of our own 
sun ; and that Alpha Centauri is one tenth the sun's mass. 

A remarkable illustration of the truth of that generalization 
which extends the laws of gravity to these depths in space has 
recently been furnished. Certain minute movements of Sirius, 

* Watson : "A Popular Treatise on Comets," pp. 328, 358, 359, 361. 

\ " Toutes les parties de notre monde planetaire auraient done nne origine com- 
mune, et le systeme tout entier seraiten communication avec les systemes etraogers 
par l'intermediaire des cometes et des meteores." — Secchi: "Le Soleil," p. 383. 



1873.] Unity of the Physical World. 195 

the brightest star in our heavens, led Bessel to suspect the 
existence of a small companion-star revolving about it, and 
exerting a perturbating influence. Such companion was after- 
ward, in 1862, actually discovered by Mr. Alvan Clark, an 
American observer. 

Not only do we find stars thus swinging about in couples, 
but, in other instances, we find them grouped in threes, 
fours, and even higher systems, all rotating about a com- 
mon center. Thus, Theta Ononis, a star scarcely visible 
to the naked eye, in the celebrated nebula of Orion, resolves 
itself, under the telescope, into seven mutually connected 
suns. 

Another stellar phenomenon of great interest, though not as 
yet demonstrably explained, is that of variable stars. Though 
numerous cases of irregular variability are known, we refer here 
to such stars as increase and decrease in brightness through 
regular periods, like the celebrated stars Mira in the whale and 
Algol in the head of Medusa. 

Two explanations have hitherto been offered of such phe- 
nomena. Perhaps the periodical variations are due to the 
rotation of these bodies upon their axes, combined with un- 
equal luminosity on different sides. * Perhaps they are 
caused by partial occupations by dark planetary bodies 
revolving about them. Both these explanations equally pre- 
sume the existence of movements in the depths of space, 
which can only be regulated by the laws of central forces 
which hold such imperial sway within the limits of our own 
system. 

More recently, variability has been attributed by M. Faye f 
to the effects of different phases of refrigeration. Father 
Secchi,;j; and after him M. Stanislaus Meunier,§ connects vari- 
ability with the phenomenon of " spots " so well known as 
marking the surface of our sun, and, by their regular increase 
and diminution through intervals of about ten years, imparting 
a variable character to the solar light. These physicists main- 

* Zollner, Stewart, Klinkerfues. This explanation requires regularity in the 
periodicity of the stars. 

f Faye: " Revue des Cours Scientifiques" t. iii, p. 617. 
% Secchi: "Op. Cit.," pp. 404-5. 
§ Meunier: " Op. Cit," p. 160. 



196 Unity of the Physical World. [April, 

tain that spots, periodicity and total disappearance of stars, are 
but different degrees of one phenomenon, and that they are 
caused by a diffusion or eruption of heated currents from the 
central non-luminous and more highly heated portion, through 
the photospheric, partially cooled envelope. The plausibility 
of this explanation rests on the truth of Secchi's theory 
(adopted and elaborated by Faye) of the gaseous and non- 
luminous condition of the solar nucleus. Should this expla- 
nation prove true, the) phenomenon of variability still serves 
as a link of connection between our system and the remotest 
regions of space, since, by all admissions, our sun is a variable 
star.* 

(4.) Firmamental movements. Nearly all the stars called 
" fixed " are in actual motion. They do not all move with 
uniform apparent velocity, nor in a uniform direction. These 
movements, moreover, are, to our^eyes, extremely slow. To 
travel across a space in the heavens equal to the apparent 
diameter of the moon's disc, would require from 300 to 1,500 
years and upward. Of course, nothing can be known of the 
actual velocity of these motions, except in the case of stars 
whose distances have been determined. The following are 
examples of these : Arcturus moves 54 miles a second ; 61 
Cygni, 40 miles ; Capella, 30 ; Sirius, 14 ; Alpha Centauri, 13 ; 
Yega, 13 ; Polaris, 1^. For purposes of comparison, we may 
state that the earth moves in her orbit with a mean velocity 
of nineteen miles a second; the other planets, with velocities 
varying from three to thirty miles a second ; and the sun has a 
proper motion in space (as we shall presently explain) of about 
four miles a second. 

Thus the stars called "fixed," and which are used as points 
of comparison for all our observations on the motions of the 
planets, are themselves in perpetual motion. In consequence 
of their unequal motions, certain stars will travel, in the course 
of time, out of the constellations with which astronomy has 
identified them for three thousand years. 

Isolated and unconformable movements among the stars 

* Proctor: "The Sun," pp. 197-9; Secchi: "Le Soleil," pp. 113-117; Cham- 
bers: "Desc. Astron.," pp. 14, 15; Loomis: "Sun Spots," etc., in "Amer. Jour. 
Sci.," [2,] vol. 1, p. 153, et seq. We are indebted to the patient observations of 
Schwabe of Dessau for this determination. 



1873.] * Unity of the Physical World. 197 

might not clearly appear referable to the same physical causes 
as we find acting within the limits of our system. Proctor,* 
however, has clearly shown that groups of stars are character- 
ized by a common " drift." Not all the stars within a circum- 
scribed space can be reasonably imagined to sustain a physical 
connection with each other, since many of those which, to our 
eyes, are most closely approximated, may be at enormously 
unequal distances. Such, however, as manifest a common 
motion, may fairly be regarded as moving under uniform con- 
ditions. Even this, however, does not demonstrate that those 
conditions are reproduced in the solar system ; but the sugges- 
tion is probable. 

Again, our own sun is one of the stars manifesting a proper 
motion. This motion is revealed by the slow opening of the 
ranks of the stars in one part of the heavens, and their gradual 
closing together in the opposite quarter. Such apparent mo- 
tions of the stars remain, after making all allowance for their 
real motions. Thus our sun is traveling onward, with all his 
retinue of planets and satellites, toward a point in the constel- 
lation Hercules, and at a rate of 153,000,000 miles a year. 
Astronomers are of the opinion that this proper motion of the 
sun is directed in an orbit whose center is in the Pleiades, 
and whose circumference is so vast that 18,200,000 years are 
required for a single revolution. 

This probable revolution of the solar system about a center 
within our firmament renders it probable that the proper mo- 
tions of the other stars are also due to orbital movements about 
the same center. Thus we shall be led to contemplate the 
starry firmament w r ith its 77,000,000 of suns, as an example of 
a solar system on a more stupendous scale. 

There is still another order of stellar existences to which at- 
tention ought to be directed. More than &\q thousand nebul© 
have already been laid down on the map of the heavens. 
Their ordinary appearance is that of a faint luminous cloud 
spread on the dark background of the sky. Yery many of 
these, subjected to the scrutiny of the telescope, resolve them- 
selves into stars and " star-dust," or minute points of light. 
Others defy all power of resolution. 

It seems quite certain that some of the nebulae lie within 

* Proctor: "Other Worlds than Ours," pp. 277-281; "The Sun," pp. 428-9. 

Fourth Series, Vol. XXV.— 13 



198 Unity of the Physical World. [April, 

the limits of our firmament of stars. The tendency of some 
modern astronomers is to the opinion that all the nebulas are 
confined to distances no greater than the stars. Should this 
opinion become established, there are still some phenomena 
presented by the nebulae which seem to indicate central gravi- 
tation and rotary motion. While many are more or less ir- 
regular, others present a spherical (or at least a circular) form. 
Others are beautifully annular. Still others, as the nebula in 
Argo, present parabolic curves resembling the tails of comets ; 
and others, finally, like the nebulas in Canes Yenatici and 
Yirgo, are strikingly spiral. All these forms are irresistibly 
suggestive of central forces and axial rotations. 

But the common opinion of astronomers seems to be in ac- 
cord with that of the Herschels, that probably very many of 
the nebulas are really other firmaments of stars wholly exter- 
nal to ours, and removed to distances proportionate to the vast 
interstellar spaces of our own firmament. Our firmament, ac- 
cording to the system of gauging the star-depths employed 
by Sir William Herschel, is circumscribed by a definite bound- 
ary, and presents somewhat the form of a grindstone cleft 
around a portion of its periphery. It is true that the telescope 
reveals a multitude of stars not seen by the unaided eye ; and, 
as the power increases, star after star rises in the far-off hori- 
zon of our view, till it would seem that the number is infinite 
and boundless. But our firmament has its outer periphery. 
When the most powerful instruments are steadily turned to- 
ward even the most populous portion of the sky, the vision 
threads its cold and devious way from rank to rank of glitter- 
ing suns, till, finally, it stands upon the outer ramparts of the 
firmament and looks out upon immensity. What solemn 
emotions fill the soul when it succeeds in traveling beyond the 
stars, and gazes through the loop-holes of the firmament upon 
the blackness and emptiness beyond ! 

But what of the realms of space beyond the boundaries of 
our star-system ? Across that dark and pathless interval the 
telescope has led our vision, and lo ! upon the remotest con- 
fines of the universe hangs a faint film of light, like the feeble 
glow of a watchman's lamp upon the shore of a cold and dark 
and trackless sea. In other quarters of the heavens are other 
patches of light, the counter existences of this. These are the 



1873.] Unity of the Physical World. 199 

nebulas ; and such, according to current views of stellar as- 
tronomy,* are their relative positions and distances. 

Should such views be finally confirmed, we shall discover 
still stronger analogies with the phenomena of the solar sys- 
tem, and stretching over intervals of space too vast for even 
the imagination to span. 

There is good ground for doubting, however, whether mere 
clouds of luminous vapor, which most of the irresolvable 
nebulas are supposed to be, would be visible to human eyes if 
really so far external to our firmament. Since some of the 
irresolvable nebulous matters have shown such a connection 
with stars as to demonstrate that they belong to our stellar 
system, it may be most reasonable to assume that all irresolv- 
able nebulas are thus associated. Accordingly only resolvable 
nebulas would be regarded as external, while the irresolvable 
nebulas would be only specimens of formative matter in various 
stages of differentiation. This view is sustained by the existence 
of so called nebulous stars and planetary nebulas, in which the 
irresolvable nebulous matter presents itself condensed toward 
the center into a state of greater luminosity, which, in many 
examples, approaches or reaches the appearance of a veritable 
star or couple of stars. f 

(5.) Inferences from the movements of light. Whether orb- 
ital and axial motions, and other evidences of the presence 
of gravity, be traced to the distances of the fixed stars and 
nebulas or not, this proof of community of conditions certainly 
exists, that the flight of the luminous ray proclaims identical 
laws throughout the visible universe. Light is a phenomenon 
universally regarded as arising from inconceivably but meas- 
urably rapid vibrations of a subtile material fluid commonly 
known as ether.J Wherever light penetrates there is ether. 

* Sir John Herschel: " Outlines of Astronomy,' 1 4th ed., p. 537 ; " Treatise on 
Astronomy," Am. ed., 1851, chap, xii; "Familiar Lectures on Science," p. 215; 
Nlohol: "Architecture of the Heavens," letter i; Guillemin: "The Heavens," 
p. 366. On the contrary, see Proctor: "Other Worlds than Ours," chap, xii; 
Rorison: "Replies to Essays and Reviews," pp. 270, 271 ; Whewell: "Plurality 
of Worlds," p. 142. 

f For striking examples see the figures of Delaunay : "Op. Oik," pp. 635, 636, 638. 

X Aside from the necessity of some such medium for the propagation of light, 
and, as some of the latest speculations indicate, for the propagation of electricity 
also, the evidence for the existence of an ethereal fluid rests on slight disturbances 



200 Unity of the Physical World. [April, 

To the remotest star — to the remotest nebulae — this tenuous 
fluid fills immensity ; and throughout the height and depth, 
the length and breadth of the empire of matter, this omni- 
present element is quick with the tremors generated by 
millions of suns. Light flies 186,000 miles in a second of 
time. The solar beam falls to the earth in eight and one 
third minutes, and reaches the orbit of Neptune in four hours. 
The light of the nearest star has occupied three and a half 
years in reaching us, and that of the remotest star which 
shows a parallax, seventy years. The light from the most 
distant star which shed a discernible light in the great 
telescope of Sir "William Herschel had left its source eight 
thousand years before. Eminent authorities entertain the 
belief that light from some of the distant nebulae must have 
occupied 700,000 years in reaching the earth.* 

What a conception is here for the mind to dwell upon ! 
What proof of the age of the material universe, and its extent ! 
Yet the same ether, like an ocean bathing continents on its 
opposite shores, pulsates through the systems of earth, sun, 
Arcturus, Polaris, and vanishing nebulae. " It is light," says 
Sir John Herschel,t " and the free communication of it from 

in the movements of certain comets of short period, especially Encke's. Mr. A. 
Hall (" A.mer. Jour. Sci.," [3,] ii, p. 404) has recently raised a doubt in reference to 
the correctness of the explanation of the retardation of Encke's comet. Professor 
W. Stanley Jevons, also, in a late number of the London "Chemical News," at- 
tributes the retardation of the comet to electricity, and regards the hypothesis of 
a resisting medium as entirely imaginary. It is worthy of consideration, however, 
that the ethereal fluid, if it possess the properties of matter, must be increased in 
density and resisting power in the vicinity of great masses of matter, especially 
the sun; and that, hence, other things being equal, those comets having the short- 
est perihelion distances will experience the greatest effects. It is also worthy of 
remembrance that possibly the uniform motions of the planets about the sun may 
have imparted a vortical movement to the ether, which would accelerate or retard 
the motions of comets in accordance with their relation to the direction of the 
ethereal current. This would diminish its effect on all the comets of short period, 
since they all have direct motion. Ic must not be presumed, however, that this 
fluid is necessarily subject to the law of gravitation, and is possessed in every re- 
spect of the properties of ordinary matter. The nature of the ethereal medium, 
which the almost unanimous judgment of physicists holds to exist, is, at the pres- 
ent moment, the object of the profouudest researches and speculations. (Sir John 
Herschel : "Familiar Lectures on Scientific Subjects," lect. viii; Mac Vicar: "A 
Sketch of a Philosophy," parts ii, iii.) 

* Guillemin: "The Heavens," p. 366. 

\ Sir John Herschel: " Familiar Lectures," p. 218. 



1873.] Unity of the Physical World. 201 

the remotest regions of the universe, which alone can give, and 
does fully give us, the assurance of a uniform and all-pervading 
energy — a mechanism almost beyond conception complex, 
minute, and powerful, by which that influence, or rather that 
movement, is propagated. Our evidence of the existence of 
gravitation fails us beyond the region of the double stars, or 
leaves us, at best, only a presumption, amounting to a moral con- 
viction, in its favor. But the argument for a unity of design 
and action afforded by light stands unweakened by distance, 
and is co-extensive with the universe itself." 

(6.) Revelations of the spectroscope. The culminating proof 
of identical conditions throughout the physical universe has 
been furnished by the spectroscope. This little instrument, 
of recent invention, takes the slender ray of light admitted 
through a narrow slit, and subjects it to a peculiar scrutiny 
— a searching examination, which extorts from it the secret 
of its origin, and of the body which sent it forth, and of the 
medium through which it has traveled. We can offer but a 
few words of explanation of this mysterious process, referring 
to the works of Schellen, Roseoe, Huggins, Lockyer, Brewster, 
Angstrom, and others, for fuller information. 

Every one knows that solar light passed through a prism 
of glass undergoes decomposition into its seven primary colors, 
which may be projected on the opposite wall. Under proper 
adjustments this colored spectrum may be seen crossed by nu- 
merous dark lines. Light proceeding from other luminous 
sources presents other phenomena. The results of extended 
experiments upon artificial lights have established the three 
following principles: 

1. The spectrum of an incandescent solid or liquid is con- 
tinuous, that is, it presents no lines across it. 

2. The spectrum of a glowing vapor or gas is crossed by 
numerous bright lines, and each different vapor gives a differ- 
ent set of bright lines. 

3. The spectrum of an incandescent solid or liquid shining 
through a vapor (dark or incandescent) of lower temperature 
than the source of the light is crossed by numerous dark lines, 
and these dark lines occupy the same positions as the bright 
lines proper to the spectrum of the vapor. 

From the third law it appears that vapors transmitting light 



202 Unity of the Physical World. [April, 

from an incandescent solid or liquid, absorb exactly the same 
rays which they would themselves emit if incandescent. Light 
shining through the vapors of sodium presents a certain set of 
dark lines ; but if the vapors of sodium are rendered incan- 
descent, they produce a set of bright lines occupying exactly the 
places of the dark ones. This set of dark lines across any 
spectrum becomes, therefore, the evidence of the presence of 
sodium in the vapors through which the light passes. 

Now, dark lines, as we said, cross the spectrum of the sun. 
This, first of all, proves that the light of the sun emanates from 
an incandescent solid or liquid, and passes through vapors of 
lower temperature in escaping to the earth. How sudden and 
unexpected a revelation of its constitution ! A liquid nucleus 
with an envelope of glowing clouds* 

But certain ones of these dark lines occupy exactly the posi- 
tions of the bright lines of the spectrum of sodium. The vapor 
of sodium is therefore present inline gaseous envelope of the 
sun ! Sodium is one of our most common substances. It is 
the basis of common salt consumed at every human meal. It 
gives the saltness to the waters of the universal ocean. This 
most familiar element enters largely into the constitution of the 
sun. 

But another set of the dark lines of the solar spectrum corre- 
sponds to the bright lines of the spectrum of hydrogen. Now 
hydrogen is one of the two constituents of all the water which 
belongs to our planet. It is also a constituent of coal, of 
petroleum, and of all vegetable and animal substances. This 
familiar element abounds also in the sun ! 

Nor is this all. Physicists have studied these magical lines 
of the solar spectrum until they have detected the existence of 
sundry other substances in the constitution of the sun. We 
find there not only sodium and hydrogen, but iron, magnesium, 
barium, copper, zinc, calcium, chromium, nickel, and prob- 

* Father Secchi does not regard the liquid nucleus fully proven. The dark 
spectral lines would result if the photosphere of the sun were in such a state of 
condensation as to present an analogy to mist, and thus shine as a liquid ; while 
the absorbent medium might be a non-luminous atmosphere external to the photo- 
sphere. Thus the central portion of the sun might be a non-luminous gas, (Secchi : 
"Op. Cit.," pp. 104-6.) Though this theory is adopted by M. Faye, ("Comtes 
rendus," 16 and 23 Jan., 1865 ; 27 July, 1868, torn, lxviii, 197,) we feel con- 
strained to regard the doctrine of a molten nucleus the most plausible. 



1873.] Unity of the Physical World. 203 

ably, also, cobalt, strontium, cadmium, and potassium. These 
include nearly all our common elements. Iron is disseminated 
through all the rocks, and, in places, is accumulated in mount- 
ain masses. Calcium is the basis of chalk and all limestones, 
and enters into the constitution of a large proportion of the 
other rocks. Magnesium, under the guise of dolomite, consti- 
tutes extensive geological formations, and enters, besides, as a 
common constituent, into other minerals and rock-masses. 
Verily, it would seem that earth and sun have been molded 
out of the same lump of material. "Were earth a daughter of 
the sun, she could not more completely have inherited the 
traits of her mother. 

With what breathless interest were the questionings of this 
little instrument addressed to the stars ! And how satisfac- 
torily did they respond ! Dark lines cross their spectra as in 
that of the sun. They are, then, other suns ; they shine by 
their own light ; their luminous spheres are enveloped in 
vapors, whose light-vibrations are attuned in unison with those 
excited by the spheres themselves. 

But what are the substances whose interferences silence 
certain of these starry rays? Are they known, or are they 
stranger elements? How sublimely instructive the response, 
as we see it handed down from Aldebaran and Betelguese and 
Sirius. Sodium is also there, and magnesium and iron and 
calcium. Yes, one kind of matter forms the substance of the 
solar system and the starry firmament. The dust of our streets 
is ignited to starry suns in Arcturus and the Pleiades. 

There is one step further. Will the nebulae respond to our 
interrogatories? We do not mean the revolvable nebulae for 
these, of course, will give us star-light ; * but what of the 
cloudy nebulae which stubbornly refuse to be resolved ? They 
have sent down their response ; the lines of their spectra are 

* There are, indeed, resolvable nebulae which give us bright-line spectra. Their 
separate stars are therefore merely segregated patches of the luminous vapor, 
which in many cases appears more continuous in the regions more removed from 
the center. These phenomena are full of suggestions bearing upon theories of 
stellar genesis. 

It may be as well to add that not a few celestial objects afford us a continuous 
spectrum — having neither bright nor dark lines. This is true of several dense 
star-clusters, as well as of a number of resolvable nebulas. The continuous 
spectrum may indicate that these bodies are incandescent solids or liquids, or 



204 Unity of the Physical World. [April, 

bright instead of dark / They are luminous vapors. How 
promptly and how eagerly the}' testify. How long have they 
waited for this opportunity to reveal the vastness of the ONE 
Ckeator's empire ! These cloudy nebulae are not, then, other 
firmaments of stars, but starry material to be wrought hereafter 
into firmaments. 

But what of the substance of these vapors ? We confess that 
here are phenomena which, for the present, puzzle us. The 
analysis of the thin light of a nebula is a most difficult task, 
and we are but just beginning to succeed. Still, in these reve- 
lations are two words, and perhaps three, which we recognize. 
In the (planetary) nebula of Draco are bright lines, which cor- 
respond to mitrogen and hydrogen, and one which comes very 
near to barium. 

It should be remarked, in conclusion, that the failure to 
identify any terrestrial substance in, a celestial body is not con- 
clusive proof against its existence ; since, in the case of lumi- 
nous bodies enveloped in luminous vapors, the luminosity of the 
vapor may be such that its emissive property exactly neutral- 
izes its absorbent property, so that the spectrum shows neither 
the dark lines nor the bright lines characteristic of the vapor. 

For the purpose of furnishing a convenient conspectus of the 
results attained from the spectroscopic analysis of a large range 
of luminous objects, we append to this article a table compiled 
from the leading authorities. 

Such are the principal facts which the most recent studies in 
cosmical physics have revealed respecting the unity of the ma- 
terial universe. We cannot fail to be impressed by the validity 
of the conclusion, and the importance of the lesson which it 
teaches respecting the unity of that intelligence and power and 
personality of whose will all these phenomena are the objective 
expression and interpretation. 

The phenomena which we have surveyed and reasoned about 
are all facts of co-existence. There is a co-ordinate view of 
unity in nature which presents facts in an order of succession, 
contemplating every phenomenon as a stage in a single devel- 

else, that having gaseous envelopes like the ordinary stars, these envelopes are in 
just that state of luminosity and tension which renders their emissive power equal 
to their absorbent. Such a state of vaporous luminosity would, therefore, exceed 
that of our sun. (Compare Proctor : " Other Worlds than Ours," pp. 289-292.) 



1873.] 



Unity of the Physical World. 



205 



opmental line stretching backward and onward toward eter- 
nity. Such a survey is adapted to leave upon, the mind an 
impression of the unity of the controlling Intelligence. through 
boundless time, as vivid as the glimpse we have taken is fitted 
to impress respecting the unity of that Intelligence in bound- 
less space. That survey, which- is complementary to the pres- 
ent one, and which brings us into the presence of the question 
of cosmical evolutions, must be deferred to another occasion. 



TABLE OF ELEMENTS KECOGNIZED IN THE HEAVENLY BODIES. 





DARK-LINE SPECTRA. 


Dark & 
Bright 
line. 


BRIGHT-LINE SPECTRA. 




Suni 


White Stars. 

Secchi's first 

type. 


Yellow Stars. 
Secchi's sec- 
ond type. 


Variable Stars 

Secchi's third 

type. 


Is 

■a g 


<M 1*1 


ELEMENTS. 


Reda 

Stars. 
Sec- 
chi's 
fourth 
type. 


o . 

»fcD 
c - 

si 






Sirins. 


Vega. 


Alde- 
baran. 


Pollux 


Betel- 

icuese. 


2Pe- 

gasi. 


m 


o 3 


Sodium . . . 

Iron 

Hydrogen . 
Magnesium 
Barium . . . 
Copper. . . . 

Zinc 

Calcium . . . 
Chromium . 
Nickel 

Cobalt 

Strontium . 
Aluminium. 
Cadmium. . 
Silicon 
Potassium . 
Bismuth . . 
Tellurium . 
Antimony . 
Mercury . . 
Nitrogen . . 
Carbon . . . 
Titanium . . 
Thallium . . 


* 
* 
* 

* 

* 

? 

? 2 
? 

? 2 
? 

* 


-* 

*• 
* 


* 


•5f 
* 

* 
* 

* 
•J8- 

* 


* 

* 


* 
? 


* 
1 


* 


? 


* 


* 


«• 



1 The chromosphere of the sun contains sodium, hydrogen, magnesium, and barium. 

*Secchi: "Le Soldi." 

» Secchi : " Le Soleil." 

* Huggins: "Spectral Analysis of the Heavenly Bodies." 

6 Huggins: Phil. Trans., 186S. See also ' ; Comtek rtndus," lxvi, pp. 1299 and 1336. 
8 Young: " Amer.Jour. Sci., 1 ' [3] iii, p. SO. 

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